When I was working in Indiana a local controversy arose regarding the source of high nitrate concentrations that was infiltrating from groundwater into a small tributary and then into a large surface stream. It is known that most elevated nitrate concentrations come from fertilizers or animal and human wastes. Because there was a large swine farm near that location almost everyone believed the nitrate had to come from their operations. However this feed lot was fairly well-designed and the pig wastes were captured and removed so efficiently that the pig farm owner believed it couldn’t be from his operation. Also in that same reach of the tributary were numerous homes along the stream area that were on older septic tanks. So, when they presented this dilemma to me, I suggested to the swine operations that the high nitrate water be analyzed also for caffeine, which had been recently developed as a fairly simple analysis. We moved from the area before I heard any more about this problem. However, from second hand reports I learned that they discovered the high nitrate plume also contained significant caffeine. Since pigs don’t drink much coffee and humans drink lots, the source of the high nitrate was determined to be from the septic tanks.